Oracle Interview Questions

41.What are the differences between LOV and List Item?

LOV is property whereas list items are considered as single item. List of items is set to be a collection of list of items. A list item can have only one column, LOV can have one or more columns.

42.What are privileges and Grants?

Privileges are the rights to execute SQL statements – means Right to connect and connect. Grants are given to the object so that objects can be accessed accordingly. Grants can be provided by the owner or creator of an object.

43.What is the difference between $ORACLE_BASE and $ORACLE_HOME?

Oracle base is the main or root directory of an oracle whereas ORACLE_HOME is located beneath base folder in which all oracle products reside.

44.What is the fastest query method to fetch data from the table?

Row can be fetched from table by using ROWID. Using ROW ID is the fastest query method to fetch data from the table.

45.What is the maximum number of triggers that can be applied to a single table?

12 is the maximum number of triggers that can be applied to a single table.

46.How to display row numbers with the records?

Display row numbers with the records numbers –
Select rownum, <fieldnames> from table;
1 Select rownum, <fieldnames> from table;
This query will display row numbers and the field values from the given table.

47.How can we view last record added to a table?

Last record can be added to a table and this can be done by –
Select * from (select * from employees order by rownum desc) where rownum<2;
1 Select * from (select * from employees order by rownum desc) where rownum<2;

48.What is the data type of DUAL table?

The DUAL table is a one-column table present in oracle database. The table has a single VARCHAR2(1) column called DUMMY which has a value of ‘X’.

49.What is difference between Cartesian Join and Cross Join?

There are no differences between the join. Cartesian and Cross joins are same. Cross join gives cartesian product of two tables – Rows from first table is multiplied with another table which is called cartesian product.
Cross join without where clause gives Cartesian product.

50.How to display employee records who gets more salary than the average salary in the department?

This can be done by this query –
Select * from employee where salary>(select avg(salary) from dept, employee where dept.deptno = employee.deptno;
1 Select * from employee where salary>(select avg(salary) from dept, employee where dept.deptno = employee.deptno;

51.What are the components of physical database structure of Oracle database?

Components of physical database structure are given below.

4 One or more data files.
5 Two or more redo log files.
6 One or more control files.

52.What are the components of logical database structure in Oracle database?

Components of logical database structure.

7 Tablespaces
8 Database's schema objects

53.What is a tablespace?

A database contains Logical Storage Unit called tablespaces. A tablespace is a set of related logical structures. Actually a tablespace groups related logical structures together.

54.What is a SYSTEM tablespace and when it is created?

When the database is created in Oracle database system, it automatically generate a SYSTEM named SYSTEM tablespace. The SYSTEM tablespace contains data dictionary tables for the entire database.

55.What is an Oracle table?

A table is basic unit of data storage in Oracle database. A table contains all the accessible information of a user in rows and columns.

56.In the Oracle version 9.3.0.5.0, what does each number shows?

Oracle version number refers:

9 9 - Major database release number
10 3 - Database maintenance release number
11 0 - Application server release number
12 5 - Component Specific release number
13 0 - Platform Specific release number

57.What is bulk copy or BCP in Oracle?

Bulk copy or BCP in Oracle, is used to import or export data from tables and views but it does not copy structure of same data.
The main advantage of BCP is fast mechanism for coping data and you can also take the backup of data easily.

58.What is the relationship among database, tablespace and data file?

An Oracle database contains one or more logical storage units called tablespaces. These tablespaces collectively store whole data of databases and each tablespace in Oracle database consists of one or more files called datafiles. These datafiles are physical structure that confirm with the operating system in which Oracle is running.

59.What is a snapshot in Oracle database?

A snapshot is a replica of a target master table from a single point-in-time. In simple words you can say, snapshot is a copy of a table on a remote database.

60.What is the difference between hot backup and cold backup in Oracle? Tell about their benefits also.

Hot backup (Online Backup): A hot backup is also known as online backup because it is done while the database is active. Some sites can not shut down their database while making a backup copy, they are used for 24 hour a day, 7 days a week.

Cold backup (Offline Backup): A cold backup is also known as offline backup because it is done while the database has been shutdown using the SHUTDOWN normal command. If the database is suddenly shutdown with a uncertain condition it should be restarted with RESTRICT mode and then shutdown with NORMAL option.
For a complete cold backup the following files must be backed up.
All datafiles, All control files, All online redo log files(optional) and the init.ora file (you can recreate it manually).

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